How best to show a document preview

I have a fairly basic web form that gathers information such as name, address, description, yada, yada. I have to do a rewrite and so am wondering what the best practice currently is to show a preview? Right now, you click "save and preview" and go to the next page to see a preview. I can think of other methods, such as showing the preview in a pane on the same screen as the form, or show the preview in a popup window or an overlay.

What is the recommended best user experience to display a preview after completing a form that is used to generate a final document?